When Wilma exits the bedroom to look for Fred, the bed has a blue blanket on top. In the next shot when Fred is going into the room, the blanket is gone and there's a white bed sheet on top. Then when Fred is in the bedroom, the blanket is back on the bed.
The hospital Pebbles is born in must be very accommodating. Not only do they dress Pebbles, as commented by Wilma, but they also fix Pebbles' hair, complete with a bone in it. Again, it's a cartoon, and due to societal norms of the time, the real truth about childbirth and "where babies come from" was a taboo subject for TV at the time (and later on as a kids cartoon).
Pebbles, a newborn baby who is presumably only a couple of hours old at the most, is able to say "Yabba Dabba Goo" when it takes babies at least a year or two to say any words.